Earth is now outside most of the “planetary boundaries” under which human civilization emerged

Why it matters: Most discussions surrounding climate change and humanity’s environmental impact focus on factors like ice cover and global average temperatures. However, a recently published investigation examines a broader range of factors to illustrate how civilization is headed into uncharted territory compared to the last several thousand years.

According to a recently published analysis based on numerous studies, Earth has crossed six out of nine environmental boundaries that have maintained the conditions under which human civilization developed. The examination attempts to take a broad view of how the planet is changing in ways modern societies have never experienced.

Climate change – the most heavily discussed aspect of humanity’s ecological influence – is only one factor upsetting the conditions that have endured on Earth for roughly the past 10,000 years. Others, such as biodiversity, forest cover, freshwater availability, and biogeochemical flows (the relationship between freshwater, the ocean, and soil), are also far outside the norms established during this period.

The term “Holocene” describes the relative stability in the planet’s temperature and environment since the end of the last ice age around 10,000 years ago. The entire history of complex human civilization, including agriculture and the construction of cities, has occurred in this period. Scientists have used nine “boundaries” to define the circumstances conducive to this development, and all have been at risk since the beginning of the Industrial Revolution.

In the diagram above, the green zones represent conditions modern humans are accustomed to, while the red areas show crossed boundaries. The darker red coloring shows which areas are at the most significant risk. The extreme ends of the chart are blurred because researchers either don’t have enough information about them or don’t know how abnormal the situation can become.

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Biosphere integrity concerns biodiversity and is the area facing the most significant risk. Studies indicate land use by humans caused the rate of species extinctions to rise above normal Holocene levels in the late 19th century, while explosions in population and food production starting in the 1960s worsened the problem. However, the analysis stresses that overpopulation isn’t the issue. Human civilization can theoretically feed 10 billion people with proper adjustments while sustaining a stable environment.

One area where the potential risks of human intervention remain largely unknown pertains to artificial substances such as microplastics, nuclear materials, and various chemicals. While there has been significant discussion about the adverse effects these substances could have on human health and the environment, their capacity to threaten the habitability of the Earth remains unclear. These artificial materials’ long-term consequences, ecological impacts, and interactions with natural systems are subjects of ongoing research and concern.

Ozone levels represent a case where humans successfully reversed conditions toward Holocene norms. Since the ratification of the Montreal Protocol in 1987, ozone depletion rates have recovered and today are only beyond safe boundaries over the Antarctic and southern high latitudes during the spring. Scientists say this and other factors prove it isn’t too late to act.